Decomposition And Release Characteristics Of Incorporated Rice Straw And Influence On Nitrogen Use In Rice Under Different Tillage Patterns

There would be a big difference of straw decomposition and nutrition release between no-tillage and conventional tillage.Therefore field and spot experiments were conducted to study the decomposition and release characters of incorporated straw under different tillage patters with Jinyou 253 in 2006 and 2007.At the same time,¹⁵N tracer method was used to quantify the fate of nitrogen from incorporated straw.The results were showed below:The main components of straw are semi-cellulose,cellulose,and lignin, with the contents of 41.42%,31.28%and 6.20%respectively.The residue of semi-cellulose and cellulose with the average decomposition rates of 0.35 g·d-1 and 0.27 g·d-1,decreased sharply from 0 to 10 days,and became gently from 25 to 40 days after retuming.The average decomposition rate of lignin was 0.034 g·d-1,which less than semi-cellulose and cellulose.Tillage patterns played different parts on the decomposition of different straw components.It had high decomposition rates and lower residue of semi-cellulose and cellulose under no-tillage,but it was not true for lignin.Potassium released quickly in the first 10 days after returning,and then became gently.Nitrogen showed a higher decomposition rate during 0 to 10 or 40 to 70 days after returning and 0 to 10 days for phosphorus,25 to 40 days for Si.It had higher decomposition rates of nitrogen,phosphorus and Si 0-100 days after returning under no-tillage patterns,except potassium.Leaf of rice straw contains more nitrogen,Si,lignin and less cellulose, potassium than stem.So there must be great difference between decomposition rates of leaf and stem.Results indicated that leaf had high decomposition rates of semi-cellulose,lignin,and lower decomposition rate of cellulose,potassium than stem.Also it had higher decomposition rates of semi-cellulose,cellulose,lignin from 0 to 15 days after returning and 0 to 15, 30 to 45 days for nitrogen and phosphorus,45 to 60 days for Si.The residue of semi-cellulose,cellulose,lignin and nitrogen in leaf were lower than stem by 41.43%,84.66%,23.26%and 17.71%respectively.It was found that 20.91%of nitrogen from incorporated straw were uptake by rice plant,31.85%remained in straw,29.55 resided in soil,4.13% washed away and 13.56%lost in other forms.The leakage loss was influenced greatly by tillage patterns and increased times under no-tillage. Nitrogen remained more in straw under no-tillage and it was disbennifit for nitrogen use from incorporated straw.But the residue in soil and the other loss were different from years. It was found that 96.61%of nitrogen,accumulated in rice plants,came from soil and fertilizer,and the other 3.39%from incorporated straw.The accumulations and rates of nitrogen from straw or soil and fertilizer were more under conventional tillage compared to no-tillage,especially in 2006, except the no-tillage treatment in 2007.It indicated that tillage pattern had certain influence on nitrogen absorption,however,no obvious influence on the rates of nitrogen from incorporated rice straw.